Compound semiconductor protection device for low voltage and high speed data lines

Abstract

The invention relates to the protection of devices in a monolithic chip fabricated from an epitaxial wafer, such as a wafer for a Group III-V compound semiconductor or a wafer for a Group IV compound semiconductor. Devices fabricated from Group III-V compound semiconductors offer higher speed and better isolation than comparable devices from silicon semiconductors. Semiconductor devices can be permanently damaged when exposed to an undesired voltage transient such as electrostatic discharge (ESD). However, conventional techniques developed for silicon devices are not compatible with processing techniques for Group III-V compound semiconductors, such as gallium arsenide (GaAs). Embodiments of the invention advantageously include transient voltage protection circuits that are relatively efficiently and reliably manufactured to protect sensitive devices from undesired voltage transients. A protection circuit can be monolithically integrated with the protected circuit or can be packaged in a separate integrated circuit.

What is claimed is:  
     
       1. A protection circuit that protects devices on a first side of a monolithic epitaxial semiconductor substrate that are coupled to a signal line from undesired transients on the signal line, the protection circuit comprising: 
       a first steering diode collection with a first anode and a first cathode, where the first steering diode collection includes at least one base-collector junction of a transistor configured as a diode, where the first anode is coupled to the signal line and the first cathode is coupled to ground, where the first steering diode collection clamps a positive voltage transient on the signal line to a first voltage, where the first steering diode collection is formed on the first side of the monolithic epitaxial semiconductor substrate; and  
       a second monolithic steering diode collection with a second anode and a second cathode, where the second steering diode collection includes at least one base-collector junction of a transistor configured as a diode, where the second cathode is coupled to the signal line and the second anode is coupled to ground, where the second steering diode collection clamps a negative voltage transient on the signal line to a second voltage, where the second steering diode collection is formed on the first side of the monolithic epitaxial semiconductor substrate.  
     
     
       2. The protection circuit as defined in  claim 1 , where the first steering diode collection comprises a plurality of base-collector transistor junctions configured as diodes, where the plurality of base-collector transistor junctions are connected in series such that a forward-biased voltage drop of the first steering diode collection is a multiple of a forward-biased voltage drop of one base-collector transistor junction. 
     
     
       3. The protection circuit as defined in  claim 1 , further comprising a breakdown diode with a third anode and a third cathode, where the breakdown diode is formed from a base-emitter junction of a transistor configured as the breakdown diode, where the third cathode of the breakdown diode is coupled to a power supply line, and where the third anode of the breakdown diode is coupled to ground, and where the breakdown diode is formed on first side of the monolithic epitaxial semiconductor substrate. 
     
     
       4. A protection circuit that protects devices on a first side of a monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate that are coupled to a signal line from undesired transients on the signal line, the protection circuit comprising: 
       a first steering diode collection with a first anode and a first cathode, where the first steering diode collection includes at least one base-collector junction of a transistor configured as a diode, where the first anode is coupled to the signal line and the first cathode is coupled to ground, where the first steering diode collection clamps a positive voltage transient on the signal line to a first voltage, where the first steering diode collection is formed on the first side of the monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate; and  
       a second monolithic steering diode collection with a second anode and a second cathode, where the second steering diode collection includes at least one base-collector junction of a transistor configured as a diode, where the second cathode is coupled to the signal line and the second anode is coupled to ground, where the second steering diode collection clamps a negative voltage transient on the signal line to a second voltage, where the second steering diode collection is formed on the first side of the monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate.  
     
     
       5. A protection circuit that protects devices on a first side of a monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate that are coupled to a signal line from undesired transients on the signal line, the protection circuit comprising: 
       a first steering diode collection with a first anode and a first cathode, where the first steering diode collection includes at least one diode junction, where the first anode is coupled to the signal line and the first cathode is coupled to ground, where the first steering diode collection clamps a positive voltage transient on the signal line to a first voltage, where the first steering diode collection is formed on the first side of the monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate; and  
       a second monolithic steering diode collection with a second anode and a second cathode, where the second steering diode collection includes at least one diode junction, where the second cathode is coupled to the signal line and the second anode is coupled to ground, where the second steering diode collection clamps a negative voltage transient on the signal line to a second voltage, where the second steering diode collection is formed on the first side of the monolithic epitaxial gallium arsenide (GaAs) semiconductor substrate.